I have 100 but it's being read as 24?

Where is it registering incorrectly?

When it's in my inventory and my vault, it shows 100. On the "other currencies" page and in Louis' shop, I'm told I only have 24.

Did you turn them into Louis? You can do that HERE.

Ah thank you! I wasn't prompted to do that before; sorry for the newbie confusion. Though where I had 100 hearts, it now stacks with the 24 I didn't have previously?

Chances are that at some point you had turned in 24, so they should stack in the shop :)